Interlaced Column-Row Message-Passing Schedule for Decoding LDPC Codes

This paper investigates efficient decoding algorithms for LDPC codes. Alternating column-row message-passing (ACRMP) and Interlaced column-row message-passing (I-CRMP) schedules for decoding of LDPC codes are proposed and investigated in this work. Existing serial scheduling schemes for LDPC decoding are based either on column message-passing (MP) or row MP, and roughly converge twice as fast as Gallager's flooding-based MP schedule at high signal-to-noise ratio (SNR). To further accelerate the convergence speed of serial decoders, hybrid column-row MP schedules that perform multiple message passes between check and variable nodes within or between iterations are proposed. Our proposed I-CRMP schedule converges in less than half the number of iterations compared to the best existing serial decoding schedules. Compared to column MP, the added complexity of this scheme is proportional only to check-node-degree times more additions at variable nodes. This increase in complexity is moderate compared to the convergence acceleration factor that the scheme achieves. Superior performance of the proposed I-CRMP scheme is confirmed by decoding randomly generated as well as IEEE 802.11n/ac LDPC codes.